1. Field of the Invention
The present invention relates to an image-pickup apparatus, such as a video camera, which controls a focus lens.
2. Description of the Related Art
Autofocus (AF) methods include a contrast (climbing) AF method which is practically used. In the contrast AF method, a high-frequency component (hereinafter referred to as an AF evaluation value) is extracted from an image-pickup signal output from an image-pickup element and a lens position where the AF evaluation value becomes the largest is detected to perform an in-focus operation.
A video camera has been disclosed which has a focus-effect function, that is, which is capable of performing “effect photography” such as “focus-in”, “focus-out” and “rack focus (or shift focus)” by utilizing this type of AF method (see Japanese Patent No. 2702968). The focus-in is an operation of focusing gradually from an out-of-focus state, and the focus-out is an operation of defocusing gradually from an in-focus state. These focus-in and focus-out are used in depicting a scene of childhood recollections, dream sequence and a scene of reminiscence.
Further, the rack focus is an operation of intentionally shifting the focal point from a near object to a far object or from the far object to the near object, which is used in providing a visual effect such that the focal point in the image-pickup area is changed to lead viewer's eye.
In the above-described conventional example, to perform the focus-in, the focus-in operation is activated by changing over to the contrast AF after an out-of-focus state is realized by manual focus. However, in the contrast AF, the out-of-focus state is of a low AF evaluation value, so that it is necessary to find out a maximum value of the AF evaluation value from the beginning.
Further, since there is a difference in variation of the AF evaluation value depending on the contrast of an object, an in-focus state is not achieved in a constant time, thereby making it impossible to manage an effect-generating time. In the case of the rack focus as well, the contrast AF requires a climbing operation for finding out an adjacent position where a maximum value of the AF evaluation value is obtained, thereby making it impossible to manage the effect-generating time. As described above, there is a case where the focus-in is attained earlier depending on an object while there is a case where the focus-in is not attained smoothly.
Further, in the above-described conventional example, the focus-out operation is activated by moving a lens position to a near side in a case where the focus lens is located at an infinite side and by moving the lens position to the infinite side in a case where the focus lens is located at the near side. However, if the lens position is at the center or in the vicinity thereof, the lens is not always moved in an out-of-focus direction without fail.